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Message-ID: <92dcf735-6e9c-48dc-a020-d4e2658dff19@gmail.com> Date: Fri, 8 Dec 2023 15:19:28 -0800 From: Kui-Feng Lee <sinquersw@...il.com> To: David Ahern <dsahern@...nel.org>, thinker.li@...il.com, netdev@...r.kernel.org, martin.lau@...ux.dev, kernel-team@...a.com, davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com Cc: kuifeng@...a.com, syzbot+c15aa445274af8674f41@...kaller.appspotmail.com Subject: Re: [PATCH net-next v2 1/2] net/ipv6: insert a f6i to a GC list only if the f6i is in a fib6_table tree. On 12/8/23 14:43, David Ahern wrote: > On 12/8/23 12:45 PM, thinker.li@...il.com wrote: >> From: Kui-Feng Lee <thinker.li@...il.com> >> >> Check f6i->fib6_node and hlist_unhashed(&f6i->gc_link) before inserting a >> f6i (fib6_info) to tb6_gc_hlist. >> >> The current implementation checks if f6i->fib6_table is not NULL to >> determines if a f6i is on a tree, however it is not enough. When a f6i is >> removed from a fib6_table, f6i->fib6_table is not reset. However, fib6_node >> is always reset when a f6i is removed from a fib6_table and is set when a >> f6i is added to a fib6_table. So, f6i->fib6_node is a reliable way to >> determine if a f6i is on a tree. > > Which is an indication that the table is not the right check but neither > is the fib6_node. If expires is set on a route entry, add it to the > gc_list; if expires is reset on a route entry, remove it from the > gc_list. If the value of expires is changed while on the gc_list list, > just update the expires value. > I don't quite follow you. If an entry is not on a tree, why do we still add the entry to the gc list? (This is the reason to check f6i->fib6_node.) The changes in this patch rely on two indications, 1. if a f6i is on a tree, 2. if a f6i is on a gc list (described in the 3rd paragraph of the comment log.) An entry is added to a gc list only if it has expires and is not on the list yet. An entry is removed from a gc list only if it is on a gc list. And, just like what you said earlier, it just updates the expires value while an entry is already on a gc list.
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